The Mystery of Flight

The Mystery of Flight provides the reader with a clear and concise understanding of aviation. The book portrays the excitement and wonder of flight through the use of descriptive paragraphs. These excerpts convey to the reader a sense of what it is like to fly various types of aircraft. The theme of the book focuses on how man is capable of flight. In addition, the book describes many of the specific skills and techniques that are necessary in order to fly safely. The Mystery of Flight is designed to stir a reader's interest in aviation and provide them with a better understanding of a very challenging profession.

TABLE OF CONTENTS

INTRODUCTION - A Prelude

CHAPTER 1 - The Mystery of Flight

CHAPTER 2 - Proper Preparation

CHAPTER 3 - Launch Time

CHAPTER 4 - The Enroute Phase

CHAPTER 5 - The Landing Phase

CHAPTER 6 - The Sky Above

CHAPTER 7 - Flying Opportunities

CHAPTER 8 - Military Tactical Flying

CHAPTER 9 - Watch the Weather

CHAPTER 10 - Rotary Wing Flight

CHAPTER 11 - Unconventional Flight

CONCLUSION - What the Future Holds

INTRODUCTION - A PRELUDE

Aviation is an expression of man's adventurous spirit. Grace, beauty and the mystery of flight are the driving force behind an age old quest to soar free from the gravitational constraints of earth. Throughout history man has been driven to discover the elusive secret of how to fly. Numerous attempts led to that one defining moment at Kitty Hawk, North Carolina on December 17, 1903. The focused persistence and ingenuity of two brothers named Orville and Wilbur Wright helped to bring about a century of aviation that has been marked by impressive growth and amazing accomplishments. From its humble beginnings on a flight that lasted less than a minute, to the present day where man can now race around the world and fly well beyond the speed of sound. The cutting edge of aviation has moved from the sandy slopes of a North Carolina beach to the lofty and spacious heights of outer space. The thrill, the challenge and the excitement of flight are an irresistible lure to the adventurous at heart. Unforgettable experiences are the fringe benefits that can be derived from a lifetime of flying.

Climb aboard a high performance tactical jet aircraft. Strap into the narrow seat and start two powerful turbine engines that will carry you swiftly skyward. Power up, as you begin a slow taxi to the duty runway. Complete the Takeoff Checklist and call for your clearance as you taxi out onto the runway. Stand on the brakes while you push both throttles full forward to their military power settings. Feel the plane squat lurch forward against the brakes as you two engines begin to howl with a raging fury. Check all of your instruments prior to brake release and commence your takeoff roll.

To a casual observer watching from a vantage point on the ground, the takeoff sequence is an impressive event.

"The sleek jet fighter roared loudly as high pressure fuel was driven forcefully into the fiery core of two straining engines. The dart shaped fuselage leapt forward, accelerating as it rolled down the sloped concrete surface of a sun bleached runway. In seconds the jet achieved its takeoff airspeed and rose effortlessly above the ground. Passing a few hundred feet in the climb, the landing gear disappeared into the jet's underbelly and the plane surged forward. Crossing the departure end of the runway, the nose of the jet pivoted sharply upward and commenced a steep vertical climb. Unbridled thrust from two, powerful turbine engines rendered the persistent pull of gravity ineffective. The sound of the engines crackled in the cool morning air. Over time the jet grew smaller and smaller in size, until it disappeared in the grasp of a hazy summer sky."

The excitement of flight can also be experienced in the high altitude world of air combat maneuvering.

"Carving aggressively through an aquamarine sky, two fighter jets maneuvered inbound for a high speed pass. Hurling past one another, the opposing jets commenced a climbing, high angle of bank turn. Each pilot fought to gain the advantage by flying with a smooth and knowing hand. Preserving lift and energy, the engagement became an orchestrated and fact paced duel performed in a three dimensional world. Engines roared powerfully, sending torrid plumes of hot gas from their tailpipes. Each pilot maneuvered for the kill as the fighting grew more intense. The two planes became entwined in a tight, high angle of bank engagement. The tight turns intensified gravitational force on both pilot and aircraft. As quickly as it began, the adrenaline filled engagement came to a decisive end. Victory was achieved with by conserving energy, anticipating an opponents next move and drawing from years of experience in the aircraft."

The thrill and excitement of flight is not necessarily confined to a high altitude, supersonic experience. The helicopter by contrast offers a unique, low level, seat of the pants ride.

"The agile helicopter raced swiftly over the brine encrusted soil of a dry desert lake bed. Banking gently to the right, the pilot steered toward a distant mountain range that rose majestically over the sun scorched valley. Beneath the fuselage an elongated shadow danced in reckless pursuit, bouncing lightly along the rocky floor of a barren desert. Two whirling rotor blades flickered brightly in the midday sun. Desert heat poured relentlessly into the helicopter, through the wide expanse of open cargo doors."

Aviation can also be defined by contrast. For example the quiet, serene experience of being in a glider as it soars silently above sun baked terrain.

"Lifting free from the runway, the glider rose steadily. The persistent tug of a long tow line helped the sleek craft climb to altitude and its operating area.

As the tow rope fell free, the glider sailed on outstretched wings, rising rapidly on an invisible current of air. The wind slipped softly around the contoured surface of a bubbled canopy as the maneuvering glider floated majestically in the clear desert air."

An even more sedate way to fly is onboard a hot air balloon. The balloon was man's earliest mode of successful flight. In this example we observe an early morning launch from a distance as the ground crew busily prepares a hot air balloon.

"A sea of unfurled fabric covered the wide expanse of a dew drenched field. Scampering urgently about, the crew worked knowingly in the dawn's meager light. Preparations to set sail were well underway. The pulsating roar of fiery propane roared loudly, as it pierced the serene morning air. Turbulent plumes of amber raced into the balloon's gaping mouth, swelling a sea of fabric. Slowly, the distended belly of a slumbering giant began to rise, fed with a diet of superheated air.

Large crescent shaped panels appeared from an ocean of rumpled fabric. Each hot burst of fire from the propone unit served as the catalyst for lift, pulling the balloon's pliant fabric higher and higher into the air. Silhouetted against the glimmering backdrop of a morning sky, the half filled balloon resembled the sloping contour of a giant tortoise shell.

In time, the canopy assumed a more discernible form. The bulbous shaped sphere grew larger and larger as it dancing with an airy fullness above the grassy field. Lifting free from the ground, the sphere swayed with a luminescent glow, tugging impatiently at straining tethers.

Three passengers quickly boarded a wicker gondola. In unison the ground crew freed all ropes, and the craft soared majestically upward into the morning sky, driven south by a gentle breeze."

In contrast to a hot air balloon, we return to the helicopter, the best example of a complex flying machine. The helicopter is a sophisticated aircraft that relies on a variety of moving parts to sustain flight. The aerodynamic components of a helicopter move at furiously high speeds, rotating in close proximity to one another. An example of a helicopter's agility and maneuverability is described below.

"A faint, almost imperceptible vibration floated through the cool morning air. Driven by shifting winds, the sensation dissipated and then grew in random intensity. Soon a noise resembling the light tap of a big drum became perceptible.

Over time, these muffled compressions became more intense, penetrating the outstretched arms of oak tree branches. The high pitched whine of rotating turbines grew stronger and stronger until the surrounding air was saturated with an ear spitting shriek.

In unison, the dense forest echoed the hammering sound of rotor blades slapping the air with contempt. Suddenly, the shadow of a helicopter appeared, dancing swiftly across the ground as it traversed a leave covered clearing. The silhouette of a helicopter appeared, descending between the outstretched branches of two large oak trees.

During its descent, the helicopter flared slightly, achieving a ten foot high hover. Without delay, the nose of the aircraft dropped and the machine accelerated rapidly, dashing across the clearing toward a distant tree line. As the craft approached the dense foliage, the pilot pulled aggressively back on the stick and commenced a nose high climb. The aircraft decelerated rapidly, exchanging airspeed for altitude. Soon, the sleek craft reached the apex of its climb, suspended motionless in space like a bird on a perch.

Like a sailfish after leaping from the sea, the helicopter began to settle while the nose of the aircraft sliced downward and passed through the horizon to a nose low attitude. Accelerating rapidly the pilot pulled back on the stick, leveling the helicopter in a high speed hover above a patch of swirling rye grass.

Momentum carried the ship across the clearing until it reached an adjacent tree line. The nose of the aircraft rose again and the narrow fuselage swung directly overhead. Without effort the agile machine cleared the tree tops, rolled sharply to the left and disappeared behind a thrashing curtain of pine boughs."

Aviation - An Overview

Aviation is the sum of man's aeronautical knowledge and skill. It is visible expression of man's adventurous spirit as he takes to the skies. Skill and success in the air is measured by how well a pilot flies an aircraft. "Air Sense" is a critical part of this equation. Air sense is the measure of a pilot's ability to perceive and grasp the subtle but important nuances relating to flight. "Air Sense" is a God given skill that can be refined and enhanced through experience.

A critical part of flying is the ability of a pilot to "feel" the aircraft on the ground and in the air. The hum of the engine, the rush of the wind and the tug of the seat are all essential external cues that provide the pilot with a better awareness in flight. A good pilot does not ignore these signals. They are a useful way to assess flight conditions, the performance of the aircraft, and the potential for any problems. Air Sense is a pilot's ability to stay mentally ahead of a fast moving aircraft.

Exceptional pilots are gifted with the ability to fly an aircraft as though it was a physical extension of their body. Flying is not a tense, rigid, or rotely sequential activity. On the contrary, good flying involves the smooth and precise application of flight controls in a timely manner. The ability to integrate these higher level aviation skills is a true measure of an aviator's talent.

In concert with skill, flying demands vigilance and discipline. Aviation by its nature is brutally unforgiving. Complacency is insidious and ever-present threat. One neglectful moment in the air can lead to the rapid termination of a pilot's life. Fatigue coupled with complacency is an even more deadly combination. To help minimize this risk, limitations are placed on how long a pilot can fly. Factors leading to aircrew fatigue must be minimized to protect both the crew and the passengers from unnecessary risk.

This book was written to provide the reader with a broad base of knowledge about aviation. The goal is to motivate and encourage individuals who possess a desire and a yearning for flight. Modern day aviation is growing at a phenomenal pace. Each year more and more people personally experience the wonders of aviation. The lure and the excitement of flight can be expressed in a variety of ways. For the earthbound, it may be as simple as watching an airplane as it races across the sky into the evening twilight.

"The setting sun flickered brightly along the silvery fuselage of a high altitude jet. Feathery contrails poured relentlessly from the depths of each engine. Cottony plumes stretched for miles across the wide expanse of a darkening sky. The underside of each contrail was painted fiery red with the uneven brushstrokes of a setting sun. As dusk approaches the jet hastens west. Slowly, the outline of its fuselage grows faint, consumed by the surreal glow of a crimson blazing sky."

Aviation for many is a way of life. Those who choose it as a profession will enjoy many memorable experiences in the air. The following chapters are designed to encourage and kindle an individual's interested. The goal is to expand the reader's knowledge and impart a better understanding of what flying is really all about. So let's strap in and enjoy the flight! It is guaranteed to be quite a ride.

CHAPTER 1 - THE MYSTERY OF FLIGHT

How an Airplane Flies

Have you ever wondered how an airplane flies? Do you often watch in amazement as a commercial jet pass overhead in a slow descent for landing? Have you ever gazed at a large widebody jet maneuvering through the air as it maintains an impressively slow airspeed?

The image of a high performance jet aircraft flying low over the ground is an awe inspiring sight. So too is the thunderous roar of a jumbo jet as it lumbers down the runway in an amazing display of power. To the casual observer a question that is often asked is how can such a large aircraft climb free of the captive forces of gravity and fly? How do the wings of an airplane create enough lift to carry an object that is so large and so heavy into the air?

Aerodynamics

To explain how an airplane flies, it is important to understand a few aerodynamic concepts. The wings of an airplane are built to create lift. Lift is the force that is necessary in order to overcome the weight of the airplane. Lift is formed when air passes over the top and bottom of a wing. The flow of air creates a pressure differential on the wing and allows the airplane to fly.

In order for an airplane to be able to fly, it must generate sufficient lift. The lift required must be equal to or greater than the weight of the airplane. Airflow over the wings is created by the power of a rotating propeller or the thrust of a turbine engine. The airplane is either pushed or pulled through the air, in order to create lift and sustain flight.

A simple way to envision how an airplane flies, is to imagine that it is being supported by a sea of molecules. These air molecules flow at different rates as they pass above and below the wings of the plane. The secret of flight is directly related to this flow of air. Let's take a closer and more detailed look at these aerodynamic concepts before our takeoff.

Relative Wind

Relative Wind is a critical component that must be present for the production of lift. "Relative Wind," is a measure of wind in relation to the leading edge of a wing. The flight path of a wing combined with the direction of the Relative Wind helps to determine the amount of lift that is being generated by the wing. As an aircraft flies through the atmosphere, it creates Relative Wind. Relative wind can be experienced on the ground for example when riding in a car as a passenger. Wind is formed as the car moves down the highway. Simply extend an arm out into the slipstream to feel that wind. On a calm day, the strength of the wind is proportional to the speed of the car.

Relative Wind is an essential part of flight and critical for the production of lift. During takeoff and landing, it is important to maximize the aerodynamic benefits of wind. That is why pilots always strive to take off and land into a headwind. Headwinds provide additional aerodynamic lift as they pass over the wing. The additional lift is not produced at the expense of fuel. Just as a headwind is beneficial for takeoff and landing, a tail wind is detrimental. Tailwinds adversely affect the efficiency of a wing during critical phases of flight, extending takeoff and landing distances.

A tailwind increases the distance that an airplane must travel down the runway before achieving takeoff airspeed. If a pilot elects to takeoff with a tailwind, the increase in takeoff distance will be directly proportional to the intensity of the tailwind. A headwind on the other hand, increases the aerodynamic performance of a wing and reduces the distance an aircraft must travel before getting airborne.

Chord Line and Angle of Attack

To further understand how an airplane stays airborne, it is important to tie the concept of Relative Wind to other aerodynamic principles that critical for the production of lift. Two of these factors include the wing's Chord Line and the wing's Angle of Attack. Refer to Figure (1), for a depiction of these concepts. The chord line of a wing is an imaginary line that runs from the center of the wing's leading edge to the very tip of its trailing edge.

Angle of Attack is the angle that is formed between the Chord Line of the wing and the Relative Wind. The Angle of Attack on a wing will vary significantly throughout a flight because of the way the aircraft is flown and how it is configured.

Weight

An airplane's weight includes its basic weight plus fuel, passengers and cargo. An aircraft is restricted by its maximum gross weight for takeoffs and landings. It can be loaded with passengers and cargo up to a certain point. The maximum gross weight of an aircraft is tied to structural limitations. Takeoff and landing weights must be computed by the pilot for each takeoff and landing. As you can see, takeoffs are not always the same. For example, if a pilot takes off using a constant power setting in a heavier aircraft, it will require a longer takeoff roll to get airborne. The reason for this is the fact that a heavier aircraft accelerates at a much slower rate. Heavier aircraft must remain on the ground longer in order to generate a sufficient airspeed/airflow over the wings before lifting off the ground.

Thrust

Thrust is a force produced by jet engines or propellers. It is necessary to overcome drag on the airplane. Thrust can be produced in a variety of ways. For example, a glider takes advantage of the thrust that is provided by another aircraft. In contrast, the thrust created by a helicopter is formed from the rotation of its rotor blades.

The pitch angle of a helicopter's rotor blades is altered during flight. As the pitch angle of the blades increases the Angle of Attack is increased. The main rotor system takes a bigger "bite" out of the air, causing the aircraft to climb or fly more rapidly.

In the case of a jet aircraft, thrust is formed when air is drawn into the intakes of a jet engine, compressed, heated under pressure and violently propelled out the back of the engine and into the atmosphere. The rapid expansion of gasses pushes the aircraft forward through the atmosphere.

Drag

Drag is a retarding force that is created as a by-product of thrust. There are two basic types of drag, induced drag and parasite drag. Induced drag is formed when a wing produces lift. As the Angle of Attack of a wing increases, induced drag grows proportionally, all the way up to the point where the aircraft stalls.

Parasite drag originates from the exposed portions of an aircraft. These surfaces include the fuselage, the engine intakes, exposed cowlings and the landing gear. Friction is created as these components are pushed through the atmosphere. The decelerating force of parasite drag varies considerably during a flight. For example, when an aircraft is configured for landing, the wing flaps are lowered along with the landing gear. A significant amount of power must be added in order to overcome resistance and the combined effects of parasite and induced drag.

Lift Revisited

As the Relative Wind strikes the leading edge of a wing, the flow of air is divided. A wing is aerodynamically designed so that as air flows over the top of a wing it must travel a greater distance than the air passing underneath the wing. This is a very important concept. Two separate streams of air must travel different distances in order to reach the trailing edge of the wing. Due to the physical properties of air, molecules in both air streams will arrive at the trailing edge of the wing, at the same time. In order for this to occur, the flow of air above the wing must travel at a faster rate than the flow of air below the wing.

As the air is accelerated, the molecules within the airmass are spread further apart. Greater distance between air molecules in the atmosphere results in lower air pressure. So, "How does an aircraft fly"? The answer to this question is based on the pressure differential that is created between the top of the wing and the bottom of the wing.

Lift occurs when the higher air pressure located beneath the wing pushes the wing upward into the low pressure region above the wing. The secret of lift is an essential part of being able to understand how an aircraft as large, heavy aircraft like the Boeing 747 is able to fly.

The amount of lift a wing can create is based on several things. These factors include the wing's Angle of Attack, the wing's rate of travel through the atmosphere, the density of the air, the wings shape and the wings area.

Angle of Attack, as previously discussed, is a measure of the angle formed by the chord line of the wing and the Relative Wind. Angle of Attack can be increased by raising the nose of an aircraft or by altering the direction of the Relative Wind.

There are limitations associated with the production of lift and how large the Angle of Attack can be. A line of demarcation is created when the wing of an aircraft is raised to the point of stall. When this angle is exceeded, lift is no longer generated, due to a degraded aerodynamic condition. As a result, the aircraft stalls. A stall occurs when the airflow over the wing becomes disturbed. Any disturbance above the wing will reduce the size and the effectiveness of its low pressure region. As a result, a wing with an excessively high Angle of Attack will quickly lose lift and cease to fly.

Angle of Attack is also be increased by modifying the shape of the wing. A unique way to accomplish this is to temporarily change the shape of the wing by lowering the flaps. As the flaps are lowered, the trailing edge of the wing pivots downward. The chordline of the wing is shifted upward and the Angle of Attack is increased, even though the nose of the aircraft has not moved.

To better understand how lift is created, it is important to realize that air behaves very much like a liquid. Both the flow of air and the flow of water possess similar physical properties. Imagine that an airplane is flying (i.e. swimming) through a large ocean of water.

A passenger onboard a moving ship for example can easily observe the ocean as it drifts past the bow. The flow of water is also visible as it swirls across a ship's rudder and provides the necessary pressure for steerage. The flow of air over and under a wing however is invisible. Because we cannot see airflow, we cannot understand it as readily, hence the term "Mystery of Flight". By take a closer look at the ocean we can visualize the flow of air. Winds shift in many directions and vary in speed, just like the currents in an ocean. Air turbulence is similar to the pitching surface of an unsettled ocean.

"Plunging steadily into the aquamarine sea, the bow of the ship thrust a mound of pristine water gracefully upward. Misty plumes of brine rose high on the wings of a swirling breeze. Hardened steel carved cleanly into a cresting wave. The bow plunged deeper, lifting translucent sheets of water upward and casting a watery curtain in a frothy rage onto the gnarled face of the sea.

The bow recoils quickly, rising high above the swells in anticipation of another powerful stroke. As it rises the sea clings tenaciously to the concave surface of a ferrous hull. Foamy white waves slap lightly against the unyielding surface of cold black steel. Lured innocently astern, the sea darkens. Strong currents lurking beneath the surface pull retreating waves into the iron grip of a swirling maelstrom. Massive whirlpools suck the ocean chaotically downward into the surging grasp of a ship's propellers. Spiral screws compress water into tightly packed vortices which are tossed violently aft. Each water contrail dissipates quickly, floating slowly toward the surface and forming the ship's wake."

Unlike our vivid picture which is depicted above, the flow of air across a wing is invisible. To see and understand aerodynamic principles, we must rely on some demonstrations that will help us understand how lift is produced.

Airflow Demonstration

To help visually display how the wind affects the performance of an aerodynamic surface, refer to the following demonstrations outlined below. These two practical examples will help you understand how lift is formed.

Begin the first demonstration by grasping a piece of typing paper with both hands. Roll the page downward and place the curled portion of the paper up against your chin. The longer portion of the paper should hang down below your lips. Now, take a deep breath and blow a steady stream of air over the top of the paper. Observe what happens. Did you expect the force of air to push the paper down? What actually happened to the paper? Why did the paper float up in response to the wind?

A man by the name of Daniel Bernoulli can help us understand the answers to many of our aerodynamic questions. Hs was a Swiss scientist who discovered Bernoulli's Principle in 1738. Mr. Bernoulli developed a theory based on the fluid properties of air. He stated that the total energy of a fluid in motion (i.e. air) must be constant at all points in a steady path. Additionally, as the velocity of the air increases, the pressure of the fluid (air) must decrease proportionately. Simply stated, faster flowing air over the top of a cambered wing has a lower air pressure than slower moving air that travels beneath it.

Due to Daniel Bernoulli's persistence and his enlightening research relating to these physical properties, he received notoriety and fame. Unfortunately for him, this came many years after his death. The ultimate compliment however is the fact that a scientific principle is named after him. The Bernoulli Principle describes how lift is produced on a wing.

Another experiment designed to help understand how lift is formed is begun by holding two sheets of notebook paper vertically. Place them approximately three to four inches apart. Lean over and blow a steady stream of air between these two pages. Note what happens. You might expect the breeze to push both sheets further apart. What actually happened? Why did the two pages move closer together?

It is necessary to refer back to the efforts of Daniel Bernoulli in order to understand these results. Air pressure differences can effect a wing in both the vertical and the horizontal plane. A low pressure area is created between both sheets of paper as the air is accelerated through the gap. High pressure air on the outside pushes the two sheets of paper together, into the low pressure region.

Maneuvering Flight

The two previous experiments help us to visually understand how lift is a byproduct of the Relative Wind. The focus of our discussion will now shift to an aircraft's flight control system and how flight controls are used to coordinate the movement of an aircraft through the air. Before an aircraft becomes airborne, it must be taxied from the flight line to the runway. Ground taxi resembles the act of driving a car down the highway. The weight of the aircraft rides on each wheel as the plane moves about in two dimensions. When an aircraft becomes airborne however, a three dimensional world is encountered and the flight controls are used to coordinate the movement of the aircraft through all three axis.

Flight control systems vary by type of aircraft. Most commercial airplanes have flight control systems consisting of a yoke, a throttle quadrant and rudder pedals. Military aircraft, utilize a stick, a throttle and rudder pedals. Flight controls in the cockpit are connected to external control surfaces by direct mechanical linkages or by electronic "fly-by-wire" systems. Flight controls are designed to physically move all of the aerodynamic surfaces on an airplane. They are assisted by the power of motors and hydraulic actuators.

Hydraulic systems and hydraulic actuators are necessary because of the high forces that are generated by the wind. The control surfaces must overcome extreme pressure while they are being forced out into the wind stream. The power that a hydraulic system produces counters this pressure and provides control. Flaps, ailerons and rudders are moved with the assistance of hydraulic pressure.

After an aircraft becomes airborne it is flown about three dimensions consisting of the lateral, longitudinal and vertical planes of rotation. They correspond to pitch, roll and yaw in an aircraft. Refer to Figure (2) for a pictorial of these control surfaces and information about each axis of rotation.

Pitch

Pitch is the movement of an airplane about its lateral axis. The stick or yoke controls the fore and aft movement of the helicopter. The primary control surface responsible for pitch is the elevator. An elevator is located on the tail along the trailing edge of the horizontal stabilizer. It is one of two moveable parts mounted on the tail.

The elevator is an aerodynamic surface that is used to alter the shape of the tail. The purpose of the elevator is to create lift and move the tail either up or down. The nose attitude of an aircraft is controlled by the vertical movement of the tail. When a pilot wishes to lower the nose of the aircraft, the stick is pushed forward. Elevator control tubes in the fuselage are connected to hydraulic actuators and the elevator is lowered in response to the stick's movement. The Angle of Attack is increased on the horizontal stabilizer, creating additional lift. The lift causes the tail to rises and the nose of the aircraft to pitch down.

The opposite occurs when the stick or yoke is pulled back. The elevator is raised and the Angle of Attack on the tail is decreased. As a result, the tail will settle and cause the nose of the aircraft to pitch upward.

Roll

Roll is the movement of an aircraft about its longitudinal axis. The lateral movement of the stick or yoke controls roll. The control surfaces responsible for roll are the ailerons. Ailerons are located on the outer edge of the wing, along the trailing edge. A mechanical or electronic linkage is used to connect the ailerons to the stick or the yoke. Both ailerons are interconnected and are designed to move in opposite directions. During a turn, the lift on one wing is increased and decreased proportionally on the other wing.

For example, if an airplane is rolled to the left, the left aileron is raised, decreasing lift on the left wing. The aileron on the right wing is simultaneously lowered, increasing lift on the right wing. The two opposing forces create roll in an airplane. The roll rate is determined by the rate of stick displacement.

Yaw

Yaw is the movement of an aircraft about its vertical axis. Yaw is controlled by inputs to the rudder pedals. The primary function of the rudder pedals is to move the tail laterally and balance the aircraft. The rudder is a control surface that is mounted on the tail. It is attached to the trailing edge of the vertical stabilizer. The rudder pedals are mechanically or electronically connected to servos that move the rudder. A rudder functions in the same capacity as an elevator. The difference is that the force of lift is horizontal instead of vertical.

For example, a pilot who wishes to move the nose of the aircraft to the left simply depresses the left rudder pedal in the cockpit. The rudder then moves to the left, creating lift on the left side of the vertical stabilizer. In response, the tail of the aircraft pivots to the right while the nose of the aircraft yaws left, in the desired direction of travel.

When an aircraft is flown through the air, the pilot rarely uses only one axis of rotation. Maneuvering flight requires the coordinated integration of pitch, roll and yaw. Flight control adjustments are all interrelated. If one control surface is moved, the other two must be changed in order to maintain the stability of the aircraft.

Slow Flight

The ability to fly an aircraft at a slow airspeed while maintaining complete control is essential. The importance of slow flight can be appreciated by watching a large airplane on final approach for landing. As the aircraft descends on the glide path it appears to be suspended in space, barely moving in relation to the ground. These amazingly slow airspeeds are conducive to a safe and more comfortable landing. A slower approach provides a pilot with many benefits such as a shorter stopping distance, reduced braking requirements and the availability of additional runway for contingencies. To fly at these significantly slower airspeeds, a physical modification of the wing must take place.

Slow flight is possible by altering the aerodynamic characteristics of a wing. Wing flaps are located along the trailing edge of each wing, near the wing root. When wing flaps are lowered, the Angle of Attack on the wing is increased creating additional lift. On some aircraft wing flaps actually increase the area of the wing. In all cases, the chord line of the wing is shifted upward by lowering flaps. Remember that the chord line is measured from the leading edge of the wing to the trailing edge. By lowering flaps on a wing, the wing's trailing edge is lowered. Because of this movement, the angle between the relative wind and the chord line is increased. So is the amount of lift generated by the wings.

An unfortunate by-product of an increase in lift is an increase in induced drag. As a result higher power settings are required to overcome the increase in drag. When wing flaps are rotated to the down and locked position, power adjustments must be anticipated in order to maintain the proper airspeed and desired rate of descent.

The aerodynamic changes that occur when wing flaps are lowered, permits an aircraft to fly at slower airspeeds without the likelihood of stall. Flaps are used for both takeoffs and landings. A half flap configuration is normally set for takeoff while a full flap setting is selected during the landing phase.

Stalls

One of the more potentially dangerous hazards associated with aviation is the possibility of stalling an aircraft in flight. Stalls are the result of excessive Angle of Attack on a wing. There are three basic types of stall, the basic stall, the accelerated stall and the approach turn stall. Pilots regularly practice entering and recovering from stalls at higher altitudes where there is ample room for less than perfect recoveries. In order for a pilot to enter a stall, the pilot reduces the power on the engines to idle while maintaining the nose attitude of the aircraft with back stick. The basic stall is the first type of stall. It is encountered when an airplane decelerates below its normal slow flight airspeed.

The aerodynamic characteristics of a basic stall result from disturbed airflow over the top of the wing. Many aircraft are designed to provide a pilot with sufficient cues when a stall is impending. The turbulence associated with a pre-stall condition often reverberates throughout an airframe. It varies in degree from very mild to extremely violent. These vibrations are known as "buffet". Buffet is a tangible warning that the aircraft is approaching a stalled flight condition. If an aircraft continues to decelerate, the leading edge of the wing will continue to rise and the Angle of Attack will increase to a point where the airplane passes through buffet and into stall.

In a stalled flight condition, the Angle of Attack on the wing has reached an extreme angle. The wing actually functions more like a barricade than an aerodynamic surface. As the flow of air over the wing becomes disturbed and separates from the wing. The end result is a reduction in the valuable low pressure region above the wing. The aerodynamic limits of the wing have been exceeded and the wing is no longer able to create the lift necessary for flight.

When a wing is stalled the nose of the aircraft will pitch forward. The wing may roll to the right or the left as the nose falls through the horizon. The most significant feature of a stall is the fact that the pilot is no longer in complete control of the aircraft. In this case he will not be able to maintain an assigned altitude. A stalled flight condition is extremely critical when flying close to the ground since altitude must be sacrificed in order to effect a successful recovery.

To recover from a stall the pilot must lower the nose of the aircraft and add power. Lift is restored by decreasing the Angle of Attack of the wing and by increasing airflow across the upper surface of the wing. A pilot quickly learns that ailerons should not be used to level an aircraft during stall recoveries. Any erratic flight control movements may further degrade the wing's ability to generate lift. Extensive aileron movement in deep stall condition will hinder the recovery. During a stall the rudder can be used for directional control since it is not stalled. It continues to be an effective control surface. Figure (3) depicts how the airflow on a wing appears when the wing is stalled.

Many tactical military aircraft are built with a critical wing. A critical wing is designed to enhance airspeed and performance on a jet. As a tradeoff, there is very little warning of stall in these types of aircraft. If these aircraft are flown to the limits of stall, they may depart controlled flight unexpectedly and tumble violently through the air, in a series of post stall gyrations.

To counter or minimize the negative effects of a stall, many aircraft are engineered so that a stall will commence at the wing root. On an aircraft, the wingroot is located at the base of the wing, the area closest to the fuselage. As you recall, the ailerons are control surfaces which control the longitudinal axis of flight. For this reason, the ailerons should be the last part of the wing that stalls.

Aerodynamic twist is a feature that is integrated into many wings to ensure that the wing root stalls first Angle of Attack on a wing with aerodynamic twist is actually greater at the wing root than at the wing tip. As a result, when a stall is encountered, the base of the wing will stall first while the outer portion of a wing continues fly in a stream of undisturbed air.

The second type of stall is an accelerated stall. The accelerated stall is not always encountered at slower airspeeds. Even under normal flying conditions an aircraft can be accelerated quickly into a stall. For example, the rapid application of back stick during a high angle of bank turn will place a greater load on the wings. Stall occurs as centrifugal forces are combined with the sudden movement of the wing into a high Angle of Attack condition.

During steep turns, power must be added to counter the effect of high wing load. The aft movement of the stick increases the Angle of Attack on the wing, which may lead to buffet or stall. An accelerated stall may occur despite the fact that the aircraft is flying at a very high airspeed. To recover from an accelerated stall the pilot simply eases the back pressure on the stick and decreases angle of bank. Erratic movements of the flight controls during a stalled flight condition will aggravate the stall and delay recovery.

A third type of stall is the approach turn stall. The approach turn stall occurs when an aircraft is "dirty", or in the landing configuration. In preparation for landing, the gear and flaps of an airplane are lowered. Induced and the parasite drag are both significantly increased. Therefore the power requirements on the airplane are much greater. When a "dirty" airplane is in a high angle of bank turn, additional power is necessary due to wing loading. The potential for an approach turn stall is favorable under a low power, high angle of bank flight condition. The approach turn stall is a particularly dangerous since it occurs when the aircraft is in the landing pattern and close to the ground.

Approach Turn Stalls occur when flight control inputs are improperly applied to an aircraft at low energy states. If an aircraft in the landing pattern is placed into a sharp turn without sufficient power, the aircraft will slow down below its recommended maneuvering speed and it will begin to descend. If the pilot attempts to compensate for a loss of altitude by raising the nose and not adding power, it will only worsen the condition.

In this case, the Angle of Attack on the high wing can increase significantly to the point of a full stall. By raising the nose of the aircraft in a slow flight condition, the higher wing will stall first and stop flying. As a result, the high wing drops from a loss of lift and the airplane rolls over on its back. Fortunately most modern aircraft are equipped with electronic warning devices that emit an aural tone when a stalled flight condition is impending. A pilot also learns to recognize the conditions associated with stall by practicing them and becoming familiar with the proper recovery procedures.

CHAPTER II - PROPER PREPARATION

Flight Planning

Before takeoff a pilot must conduct thorough flight planning. One of the first steps is to prepare a detailed flight plan. A flight plan provides a controlling agency with a detailed description of where the pilot intends to fly and what route he or she plans to take while enroute to their destination. Flight plans are filed with the Federal Aviation Administration. A flight plan includes essential information that relates specifically to the flight. Information required on a flight plan includes the type of aircraft that is being flown, the aircraft's call sign, the planned airspeed, altitude, and desired route of flight. All enroute stops are listed along with the final destination. An alternate airfield is identified if required by weather. The estimated time enroute, fuel required to destination and the total fuel onboard is also provided.

Additional administrative requirements include: the name of the pilot, the number of personnel onboard and the color of the aircraft. Figure (4) is a copy of an actual flight plan that is used by a pilot to file with the FAA. Before departure a pilot must call or visit an approved FAA facility in order to obtain weather information for the filed route of flight. The weather must also be checked for the planned destination and any alternate airfields that are required. FAA locations are called Flight Service Stations. Weather information can be accessed by computer or by telephone. Flight Service is responsible for inputting a pilot's flight plan into the FAA computer and providing pilots with applicable Notices to Airmen or NOTAMS. A NOTAM identifies any procedural changes that might affect operations at a departure, destination or alternate airfield.

Flight Service Stations are located regionally around the country and can be reached in flight by transmitting on a designated radio frequency. Flight Service Stations activate and modify flight plans and also provide enroute and destination weather updates. When a pilot calls a Flight Service Station, the call is prefaced by the name of the Station followed by the word "Radio". For example "Macon Radio" is the call sign for the Flight Service Station located in Macon, Georgia. Various Flight Service Stations monitor the same radio frequency.

VFR Flight

Before flight, there are two types of flight plans that a pilot generally files. They are the Visual Flight Rules, Flight Plan (VFR) and Instrument Flight Rules, Flight Plan (IFR). Visual Meteorological Conditions are required for VFR flight. A pilot must be able to see and avoid both the ground and other aircraft during VFR flight. For a pilot to fly under VFR, the bottoms of the cloud layer must be at least three thousand feet above the ground and there must be a horizontal visibility of three miles or better. Marginal VFR conditions exist when the base of a cloud layer are between one thousand and three thousand feet above the ground.

Some aircraft are not properly equipped with the essential instruments for IFR flight. Many civilian aircraft have rudimentary instruments that are intended for situations where a pilot inadvertently flies into the clouds. These instruments are not rated for IFR flight and are only intended for use in the event of an emergency. A pilot on a VFR flight plan should always remain clear of clouds and any instrument flight conditions.

In the event that a pilot inadvertently enters the clouds on a VFR flight, he or she must focus their complete attention on the instruments that are available in the cockpit. The attitude gyro is the primary instrument for a pilot to watch in this situation. An attitude gyro continuously displays the attitude of the aircraft in relation to the horizon.

If a pilot has inadvertently entered the clouds, they must immediately begin using an instrument scan, in order to remain oriented. The ideal next step is to reverse course and fly back out of the clouds. To do so, the pilot commences a stable, standard rate turn for one hundred and eighty degrees of heading change.

In the event that the does aircraft break out of the clouds, the pilot may elect to continue with VFR flight and circumvent any adverse weather along the course of flight. If the weather deteriorates however, a wise pilot will opt to land and wait for better flying conditions.

IFR Flight

The second type of flight plan is called an IFR flight plan. Instrument Flight Rules apply when an aircraft is flown in conditions with cloud bases less than one thousand feet AGL, and/or the horizontal visibility is less than one mile. An aircraft that is certified for instrument flight contains all of the appropriate navigational instruments that are needed to safely fly in the clouds. In order to fly in Instrument Meteorological Conditions a pilot must also have an instrument flight rating before initiating a flight in IMC flight conditions. An instrument rating is obtained by completing a certified ground school course followed by instrument flight training in a flight simulator and an aircraft. At the completion of ground training a pilot must successful complete an evaluation by flying in an instrument rated aircraft, with an FAA flight examiner onboard.

Fuel Planning

Accurate fuel management is an essential part of flying. Fuel preservation is a top priority for all pilots. To determine how much fuel is required for a flight, the pilot must make several preflight computations. The first planning step is to measure the distance that the airplane must travel to reach its filed destination. Utilizing the basic principles of time, distance and fuel flow, a fuel plan can be prepared for each leg of the flight. The following sample fuel problem is provided to help understand how a pilot computes fuel burn and determines what proper fuel load is required.

In our sample problem, an aircraft must fly 900 nautical miles to its destination. The true airspeed for the flight is computed to be 300 miles per hour and the aircraft will be flown at an altitude of 16,000 feet. The aircraft is forecast to burn 300 pounds of fuel per hour at this assigned altitude. In this example there is no wind. As a result, the aircraft is scheduled to arrive at its destination in three hours. (900 miles divided by 300 mph equals three hrs.). To compute how much fuel is required for the enroute portion of the flight, the pilot multiplies the fuel burn rate of 300 pounds per hour, by the enroute time of three hours. The total fuel required for the cruise portion of the flight is 900 pounds.

Looks pretty simple, but fuel planning is more than a single computation. The pilot must also incorporate the fuel that is necessary for start, taxi, takeoff. The higher fuel flow associated with a climb to altitude must also be factored in to the fuel plan so that the appropriate amount of fuel is carried onboard the aircraft.

For example, a commercial airliner taking off from Kennedy International Airport in New York on a Friday evening will experience extensive delays before reaching the runway. Gate holds, departure sequencing, deicing requirements are several factors that can contribute to delays. Therefore, additional fuel must be carried in order to properly account for those delays.

During takeoff and climb out, fuel consumption is significantly higher. Throttle settings in the climb are much greater and these large power demands contribute to sizable fuel burn rates. Therefore, a large amount of fuel can be burned in a relatively short period of time. Certain flight configurations can worsen this situation. The use of an afterburner on a jet engine causes fuel flow to increase astronomically. Heavily loaded aircraft use more fuel since they take longer to climb to altitude. As a precaution, pilots must take a very detailed look at all aspects of a flight and plan for the worst case scenario when estimating fuel.

Jet engines perform more economically at higher altitudes. The optimum cruise altitude for a large jet aircraft is based on its weight at level off. Air is less dense at higher altitude. Parasite drag is significantly less when compared with conditions at a lower altitude. The outside air temperature at high altitudes is extremely cold. Fuel savings are an added benefit. In contrast, extended flight at low altitudes will increase fuel consumption and adversely affect the fuel plan.

In some cases an aircraft may be flown above its optimum cruise altitude. Fuel consumption will be higher in this scenario because of higher power settings and less favorable aerodynamic conditions. It is important to understand that carrying an excessive amount of fuel in large commercial aircraft can be wasteful. Due to the added weight of this fuel, the fuel flow to the engines will be higher. The increased weight will adversely affect fuel efficiency.

Now, let's return to our fuel planning problem. But in this case we will factor in the effects of wind on fuel performance. When making fuel computations, it is very important for a pilot to use ground speed. As the name implies, ground speed is the rate that an airplane travels over the ground. In our previous scenario, we used a "no wind" computation and based our calculations on a true airspeed of 300 nautical miles per hour. Without a headwind or tailwind component, the progress of the airplane over the ground is neither impeded nor improved.

Ride the Wind

To appreciate the effect of wind on fuel consumption, let's imagine that an airplane must fly to its destination with a 100 nautical mile per hour headwind. The ground speed of the aircraft at cruise altitude will now only be 200 nautical miles per hour, instead of 300 nautical miles per hour.

True airspeed is a measure of the actual speed of the airplane as it flies through the air. The reading on the airspeed indicator is the indicated airspeed. Indicated airspeed is a measure of the dynamic pressure of the aircraft as it flies through the air. True airspeed is the plane's indicated airspeed, corrected for any variations in the density of the atmosphere and calibration errors in the gage. It is very important to note that true airspeed is not a measure of how fast an aircraft is traveling over the ground. True airspeed is an indicator of how fast the aircraft is flying through an "ocean" of air that we call the atmosphere.

When a 100 nautical mile per hour headwind is pushing against the airplane, it is slowing the aircraft's physical progress over the ground. Aerodynamically however, the wings of the aircraft are still experiencing 300 knots of dynamic pressure.

A headwind is beneficial when it comes to increasing airflow over a wing but it is detrimental when measuring progress over the ground. True airspeed and groundspeed are independent of one another and are rarely equal.

When an aircraft is flying into a headwind, the fuel plan and the estimated time of arrival must be adjusted to compensate for the negative effects of the headwind. More fuel is required to safely reach a filed destination.

We must re-compute our time enroute based on our new headwind. So, let's take the total distance to destination (900 miles) and divide it by the groundspeed. Remember that the groundspeed is now 200 miles per hour vice 300 mile per hour with our 100 knot headwind. The flight will take an additional hour and a half to reach its destination. Therefore the time of flight will now increase from 3 hours to 4 and one half hour.

To determine how much additional fuel should be carried on the aircraft to compensate for a forecast headwind, the pilot must multiply the fuel burn per hour by the additional time enroute. A fuel burn of 300 pounds per hour multiplied by an additional hour and a half of flight time is equal to 450 pounds. Our planned fuel consumption at altitude has increased from 900 pounds to 1,350 pounds due to the extra 450 pounds of fuel burn.

During the flight, actual fuel burn must be compared against the projected fuel consumption that is depicted on the fuel plan. The task must be done at regular intervals throughout the flight, to determine if a fuel surplus or a fuel deficit exists. The difference between planned fuel consumption and actual fuel consumption may vary in either direction. Contributing factors to a fuel deficit include ground delays, headwinds, alternate routing, holding and prolonged approach times.

On the positive side, fuel requirements can actually be reduced if an aircraft can takeoff quickly or an enroute tailwind component exists. Pilots do not always count on the benefits of a tailwind during flight planning however. A tailwind cannot be used in flight planning to get you to your destination. The reason for this is that the tailwind may dissipate during the course of the flight. If a pilot relies on a tail wind to get to a destination, he or she may be left "high and dry" if the wind dies down, with a lot less fuel than planned.

Pilots are required to carry a fuel reserve on each flight. The purpose for carrying reserve fuel is to provide a buffer and to compensate for unexpected fuel deficits. A fuel reserve is increased if the weather is marginal at the filed destination. Additional fuel must be carried as a contingency. If the pilot must divert to an alternate airfield for landing there will be sufficient fuel available to reach the alternate and shoot an instrument approach.

The winds actually encountered at altitude are the truth teller. It is reflected in the aircraft's progress over the ground. If a headwind is not as strong as forecast or a tailwind is stronger than anticipated, the pilot will have the luxury of a more fuel at touchdown. Refer to an example of a sample fuel plan located in Figure (5).

Refueling

Aircraft are fueled utilizing three different methods, gravity fueling, high pressure fueling and in-flight refueling. Gravity fueling is similar to putting gas in a car. The pilot simply removes the fuel cap from the top of a wing or the side of the fuselage. The fuel nozzle is placed inside the aircraft and fueling commences. Gravity fueling is also known as "Over the Wing" fueling. It is a suitable way to transfer small amounts of fuel. The preferred method for refueling an aircraft that requires a large amount of fuel is through the use of a pressure refueling system.

Pressure refueling as its name implies, involves fueling aircraft with a forced flow of fuel. The fueling hose is configured with a special fitting that attaches directly to a refueling port on the side of the aircraft. The closed system relies on a one way, high pressure valve that opens while fuel is pumped directly into the tank. The valve closes automatically after fueling is complete. Fuel pressure can be adjusted at the fuel truck in order to suit the type of aircraft that is being refueled. Pressure refueling can be conducted safely even when the engines on an aircraft are running. Military airfields have pressure refueling facilities called "Hot Pits." The "Hot Pits" are located near a taxiway so that aircraft can be quickly refueled before takeoff or after landing.

To "Hot Pit," a pilot taxies the aircraft into the fuel pits and completes the hot refueling checklist. The ground crew attaches a high pressure hose to the receptacle and refueling is initiated. An indication of positive fuel transfer is noted when the cockpit fuel quantity gage begins to increase.

Fuel is transferred into internal storage tanks that are located in various parts of the aircraft. In smaller aircraft, the fuel tanks are located inside the wings. In larger aircraft the fuel is also stored in the wings and in fuel cells located above and below the cabin. Certain military and civilian aircraft are configured with fuel tip tanks that are mounted at the end of each wing. Auxiliary fuel tanks can also be suspended from wing store stations located below the wings. Auxiliary fuel provides the pilot with the capability to fly longer distances or remain on station for longer periods of time.

The third type of refueling is in-flight refueling. In-flight refueling is used by the military to extend the flight time of aircraft after they have launched. Large refueling aircraft with extra fuel are utilized to refuel tactical aircraft. Aircraft requiring fuel must rendezvous with the "Tanker". Refueling takes place along a prescribed route called a "Track". Aircraft to be refueled are configured with fuel probes. The fuel probe is designed to plug into a long fuel hose that is suspended behind the refueling aircraft. In some cases a refueling boom is used. A crewman in the refueling aircraft flies the refueling boom down to a receptacle in the aircraft that requires fuel. In either case once the connection has been made, the fuel is transferred at a very high rate.

Fuel in an aircraft is measured by weight instead of volume. Weight is a more reliable indicator and provides a more accurate fuel reading. During maneuvering flight, fuel in an aircraft's fuel tanks will slosh around. If total fuel was measured by volume there would be erratic fuel quantity indications displayed on the fuel gage in the cockpit. Weight is a more accurate and consistent way to measure fuel in an aircraft. The gross weight of fuel is not affected by any sloshing that occurs in the tank. Therefore, it can be displayed more accurately on a fuel gage.

While on the ground, fuel levels can be measured externally. The pilot uses a dipstick to determine how much fuel is in each tank. Measurements in smaller aircraft are accomplished by inserting a dipstick into the tank via a wing refueling port. The dipstick is removed and the total amount of fuel is displayed on a graduated scale engraved on the side of the dip stick. In larger aircraft fuel is measured by using separate fuel gages located in the cockpit. During refueling the amount of fuel that is put into the aircraft is recorded and compared with the amount of fuel that is on the gage and on the fuel plan.

The Aircraft Preflight

Before each flight, a pilot must conduct a thorough preflight. The preflight checklist is used to guide a pilot and to ensure that important things on the aircraft are checked. Areas to be inspected are delineated on the checklist. For example prior to takeoff, an airplane must be checked for loose cowlings, loose or missing service caps and unfastened access panels. The condition of the landing gear is checked along with all aerodynamic surfaces, and various engine systems. Other critical areas include fuel and oil quantities, tire pressures, unrestricted movement of the flight controls, and the engine intakes, propellers and cockpit systems.

The obvious reason for a preflight is to deal with any problems that may exist before the aircraft is flown. A preflight also extends well beyond a physical inspection of the aircraft. It encompasses a detailed analysis of factors such as weather, service facilities at the destination and a proper review of all flight notices (NOTAMS). Night operations also require special preparation. At night attention must be paid to aircraft lighting, local taxi procedures and obstacle avoidance. During tactical military operations, very thorough mission planning must be conducted well in advance of the flight. A proper preflight is essential to help minimize any surprises in the air. If preflight procedures are not conducted properly or ignored altogether, dire consequences may result.

CHAPTER III - LAUNCH TIME

The Start

Before starting an aircraft, a pilot must complete the pre-start checklist. The pre-start checklist is a tool that is used to make sure that the appropriate cockpit switches are in the proper position for start. The copilot begins the process by reading a checklist item out loud to the pilot. Checklist items are visually checked by the pilot to ensure that they are configured properly. All switches are inspected to verify that they are in the correct position. After a visual confirmation, the pilot announces to the copilot the appropriate response from the checklist. The copilot monitors the pilot's response and visually cross-checks to ensure that the switch has in fact been placed in the appropriate position.

An example of a challenge and response checklist is provided. As the copilot announces "Fuel Switches," the pilot places his hand on both fuel switches and physically moves them to the on position. The pilot then reports "Number 1 and 2 - On." The copilot crosschecks to verify the fuel switches are in the correct position and then proceeds on to the next checklist item.

When the pre-start checklist is complete, the pilot starts the engine or engines. Due to the rapid succession of procedures associated with an engine start, the start procedures are done from memory. The engine is started when a starter motor is energized. The starter physically rotates the engine until a specific rate RPM is achieved. Fuel is then introduced into the combustion section of the engine and it is ignited electrically. When the engine has achieved a self sustaining RPM the starter motor is disengaged. The Post Start Checklist is then performed following engine start.

Taxi

Before taxing for takeoff, a pilot must obtain a clearance from ground control. The clearance provides the pilot with specific departure and enroute instructions. Clearance information is generated from the pilot's filed flight plan. To activate a clearance, the pilot must contact a ground controller. The ground controller will read the pilot the complete clearance. After receipt of the clearance, the pilot must resolved any questions or issues before accepting the assigned routing.

When the crew is ready for taxi, a call is made to ground control. The pilot requests clearance to taxi and is given taxi instructions along a specified route. To aid the pilot, there are detailed diagrams of all the major airports included in their flight publications. A bird's eye view of the airfield is presented in the drawing. Runway locations, taxiway designations, ramp areas and terminal buildings are all depicted based on their size and location. Refer to Figure (6) for an example of an airfield diagram. All airport runways are numbered based on their magnetic heading. Taxiways are identified by designated by using letters of the alphabet. Buildings are depicted in black and drawn according to their shape.

When a taxi clearance is issued, the controller will specify a particular route for the pilot to take to the active runway. For example, "Lobo 14, taxi to runway 19 via "A" taxiway (pronounced "Alpha"). Pilots unfamiliar with the airfield can request progressive taxi instructions from Ground Control. When progressive taxi instructions are requested, the Ground Controller provides the pilot with a series of directions as the pilot is taxiing to the runway. A pilot must remain oriented at all times during ground taxi. Frequently there is a requirement to cross active runways enroute to an assigned takeoff runway. The airfield diagram serves as an excellent road map in order to avoid any conflicts and maintain the assigned taxi route.

Taxi signs are located strategically along sides of each taxiway. Taxi signs identify the location of all runways, taxiways and parking gates. They are lit at night for easy viewing. Under darkness, taxiways are identified by blue edge lighting while all runways are marked with white edge lighting. The last 2000 feet of the runway is marked with amber lights.

To begin taxiing, the pilot must add power to the engines so that the propeller or the jet engine can begin to physically move the aircraft down the taxiway. Taxi speeds are controlled by throttle setting and brake application. Aircraft are steered using either differential braking or nose wheel steering. Small airplanes use differential braking to control direction. With differential braking, a turn is performed by applying pressure to one of the brakes. Brakes on an airplane are employed by pressing down on the rudder pedals. For example, in order to turn an aircraft to the right, the pilot must press down on the right rudder pedal. Friction created on the right brake disk causes the nose of the aircraft to pull to the right.

Larger commercial aircraft are equipped with nose wheel steering systems. A nose wheel steering system allows a pilot to manually control the direction that the nose wheel turns. A small steering wheel located in the cockpit is used to physically move the nose wheel in the desired direction of turn.

When a large commercial aircraft is parked at the gate and is ready for taxi, it is either pushed back by a ground crew using a tractor or it is powered out of the gate using thrust reversers. During "pushback" or "powerback", the taxi director signals a pilot for all movement in and around the gate area. Ground support personnel are also positioned around the aircraft to ensure that all sides of the aircraft are clear of any obstacles while the aircraft is moved. The taxi director stands where the pilot can clearly observe all of the signals that are used to direct the movement of the aircraft. A taxi director normally uses taxi wands with reflective material on them for use during the day. At night the wands are illuminated. "Wing Walkers" assist the taxi director by monitoring wingtip clearance and tail movement when an aircraft is pivoted about in a turn.

During taxi from the ramp to the runway, a taxi checklist is completed. The taxi checklist is used to prepare an aircraft for takeoff. Examples of things required on a taxi checklist include lowering wing flaps, checking flight controls for freedom of movement and preparing all cockpit systems for takeoff.

Takeoff

Approaching the runway, the pilot must complete the Before Takeoff Checklist after the aircraft is brought to a stop at the "Hold Short Line." The hold short line is a yellow line that is painted across the width of the taxiway. The pilot must stop the aircraft behind the hold short line unless clearance has been given by the tower to taxi out onto the runway. The hold short line is designed to keep aircraft a safe distance away from the active runway and landing traffic.

When the cockpit crew is ready for takeoff, the copilot contacts the tower and requests a takeoff clearance. The tower will issue one of the following clearances: "Position and Hold" which means that the pilot is cleared to taxi onto the runway and wait for a takeoff clearance. Or the pilot may be instructed "Cleared for Takeoff". In this case the pilot is cleared to taxi onto the runway and takeoff. The pilot may also be told to "Hold Short". In this case, the pilot must remain behind the hold short line until clearance to taxi onto the runway is received.

After a takeoff clearance is received, the pilot must verbally accept/repeat the clearance back to the tower, smoothly add power and taxi out onto the runway. Out of the turn, the aircraft must be aligned with the runway centerline. During the takeoff, the throttles for each engine are increased to their takeoff power setting. Several gages are monitored to ensure that the indications are in limits and the flight controls are checked for any feedback. If all of systems are "in the green," the pilot releases the brakes and begins the takeoff roll.

As the aircraft accelerates down the runway, brakes are initially used to maintain runway heading. After sufficient airspeed has been obtained the rudder becomes aerodynamically effective and nose alignment is coordinated through the use of the rudder pedals.

A Copilot's Duties

The role of the copilot during takeoff in a commercial aircraft is to back the pilot up with the appropriate takeoff calls. The copilot also monitors the cockpit gages and makes sure that the correct takeoff power is set on each one of the throttles. Takeoff power settings are determined during preflight planning. These values are calculated based on the takeoff weight of the aircraft, the ambient air temperature, the flap settings on the aircraft and the airfield elevation.

Two important airspeeds are also computed for takeoff. The first critical airspeed is called V1 or takeoff "refusal speed." Prior to V1, if there are any problems with the aircraft, the pilot will abort the takeoff by pulling the power back to idle and immediately applying the brakes and the thrust reversers. After V1 speed is reached, the pilot will no longer consider aborting a takeoff. The crew will continue with the takeoff and concentrate on getting the aircraft airborne. In cases of emergency where the aircraft must return to the field for a landing, the pilot must climb to altitude, dump fuel, turn downwind and obtain an emergency clearance for an immediate landing. Within the cockpit, a checklist delineates the appropriate steps that are to be used. The specific emergency is reviewed and the appropriate procedures initiated in order to prepare the aircraft for landing.

In terms of the takeoff sequence, the next speed of importance to a pilot is "Vr", or "rotation airspeed." When Vr is attained, the pilot pulls back on the yolk or the stick and lifts the nose of the aircraft off of the runway. As the nose pivots skyward the aircraft follows suit and flys gracefully off the runway and into the air.

Takeoff procedures may vary based on the type of aircraft being flown. Smaller airplanes and helicopters use different cockpit procedures for takeoff but the takeoff clearance and any abort criteria must be clearly defined. The following scenario is provided so that the reader can envision a complete takeoff sequence:

"A light cool breeze blew gently across the runway. The first rays of morning light poured brightly through a row of pine tree in the distance. "Turbo one five, you are cleared for takeoff on runway one nine." "Roger, Turbo one five, cleared for takeoff on runway one nine."

Viewed from the Control Tower, a growing plume of hot gas could be seen pouring from the back of two tail mounted engines. A whirlwind of heat and dust arose, racing angrily over the surface of the taxiway. The fuel laden aircraft responded begrudgingly. Laboring for a moment the aircraft wheels broke free from a persistent grasp of summer softened asphalt and the airplane rolled out onto the runway.

As the aircraft moved, bright sunlight danced along the length of its silvery fuselage. Brilliant flashes flickered intermittently from the mirrored surface of each passenger window.

The pilot pulled the throttles back to idle as weight and momentum carried the airplane through the turn. The jet pivoted about in a wide sweeping arc. Out of the turn, the aircraft continued its taxi down the runway for a short distance and coasted to a gentle stop, poised for takeoff.

Suddenly, the peaceful serenity of the morning was shattered by a harsh, earsplitting roar. Torrid plumes of hot gas spewed violently from the tapered exhaust nozzles of both engines. Intense, unrelenting heat swirled furiously backward, out over the grass covered approach end of the runway. Awakened from its slumber, the aircraft lurched forward, nose down, like a wild bronco trying to throw a hapless rider.

At brake release, the craft began rolling steadily down the runway. The pilot steadily added power, expanding the profile of the exhaust plume and driving it even higher into the air.

Slowly and deliberately the speed of the airplane began to increase. Rate of acceleration was indicated inside the cockpit by a rising airspeed indicator and the rhythmic pounding of a nose wheel rolling over expansion joints in the concrete runway. As groundspeed increased a slight shudder filled the cabin. The fuselage began rocking gently from side to side, until the nose of the aircraft pivoted slowly upward. Lifting free from the runway, the jet bounced slightly and began its upward climb."

CHAPTER IV - THE ENROUTE PHASE

Flight Following

As we have seen, a flight plan is a detailed account of a pilot's intended route of flight. It also provides both the pilot and the passengers onboard with a measure of safety. On a VFR flight, if an aircraft should have to execute a precautionary landing at a remote airfield, the flight plan would serve as a valuable starting point for any search and rescue efforts.

"Flight Following" is a very helpful method that is used to track a pilot's progress over the ground. When a flight plan is filed the pilot lists the estimated time of arrival for the flight. Shortly after takeoff the pilot activates the flight plan by calling Flight Service on an assigned radio frequency. The Flight Service representative is provided with the pilot's call sign, take off time, and filed destination. Based on this information, the flight plan is activated. After arriving at the destination airfield a pilot MUST remember to call Flight Service and close out the flight plan. The call to Flight Service may be made on the radio just prior to landing or on the ground via telephone after the flight.

Flight following ensures that an aircraft has safely reached it's filed destination. When a pilot fails to close out a flight plan, the FAA will contact the destination airport to see if the aircraft is on the ground. If the status of the aircraft cannot be determined, a search and rescue plan is initiated to help locate the overdue aircraft.

In the process of filing a flight plan a pilot must receive a thorough weather brief that covers the enroute and destination portion of the flight. If marginal weather is forecast during the scheduled arrival time, an alternate airport must be identified on the flight plan. Additional fuel must also be carried in order for the pilot to safely reach the alternate airfield.

Weather briefings can be obtained over the telephone or by visiting a meteorological facility. Automated weather stations provide briefings and weather can also be pulled up on the Internet. Weather stations are located at designated regional airports and military airfields around the country. These facilities provide face to face briefing services for pilots and aircrew.

Enroute to a Destination

When an aircraft lifts free of the runway and climbs into the sky, the pilot must concentrate on a variety of tasks. After the landing gear is raised and the flaps are retracted, the pilot must fly the assigned departure heading. When the aircraft is clear of the airport traffic area a pilot is instructed by tower to contact departure control on a radio frequency that is provided in the clearance. During the initial climb, the focus of attention must be dedicated to collision avoidance. The entire crew is tasked with the important task of searching for any conflicting aircraft.

After reaching the assigned enroute cruising altitude, the pilot's attention is focused on enroute navigation and cockpit systems. The fuel plan must be compared with the actual fuel consumption to determine whether the crew is ahead or behind on fuel.

Navigation

Proper navigation is essential for the safe conduct of flight. A pilot can utilize several navigation techniques in order to proceed to a desired destination. There are two primary methods of navigation: visual navigation and instrument navigation. Both methods are not mutually exclusive. For example, flight instruments are frequently used in conjunction with a map to crosscheck and verify the location of an aircraft.

VFR Navigation

Pilots who fly under VFR flight rules, navigate by using a map, much like a driver does as they travel down the highway. A VFR Sectional is one of many maps that a pilot uses for VFR navigation. A pilot can reference a VFR Sectional and compare distinguishing features on the ground with their symbolic representation on the map. The VFR Sectional has a map on both sides. Each side represents an area equivalent to 42,500 square miles. The VFR Sectional derives its name from the largest city depicted on the map. For example, a Phoenix Sectional covers several large populated areas but the biggest of these is the city of Phoenix.

A VFR Sectional provides a pilot with a bird's eye view of an entire area. Colors are an important aid to navigation on the map. They signify a variety of things to a pilot. For example, different shades of brown and orange are used to depict ground elevation in mountainous regions. Blue is used to display water and yellow depicts large populated areas such as cities and towns. Both man made and natural objects are represented on a VFR Sectional map. Cities, airports, roads, railroad tracks, power lines, factories, towers, quarries, lakes, rivers and restricted airspace are all depicted.

During preparation for a VFR flight, it is worthwhile for a pilot to draw the route of flight on a navigational chart. A yellow highlighter is useful for making a clear distinct line from checkpoint to checkpoint. The line helps to clearly delineate a path that should be flown over the ground. Once airborne, the route is an excellent point of reference. The pilot can use it to compare the actual position of the aircraft to where it should be along the preplanned route of flight. While navigating, a pilot will often orient the map in the direction of flight. With a map properly oriented, the objects depicted on the map are in the same relative position as they are on the ground. The pilot can tell immediately if the aircraft is off course by noting the position of the aircraft in relation to the highlighted course line.

Navigation information should also be written on the map. It is helpful to place the information in a box next to the course line, for each segment of the trip. The information that is written in the box includes the aircraft's heading corrected for the wind, the total distance of each segment, the time enroute and how much fuel is required for each leg. To be useful, this data must be readily accessible and clearly displayed. An example of a navigation route on a VFR Sectional is depicted in Figure (7).

It is important for a pilot to conduct a thorough map study before takeoff. A map study allows a pilot to become familiar with the elevation of the surrounding terrain and note if there are any significant man made obstacles that may affect the flight. The location of each checkpoint is noted along the route of flight. For a pilot, the navigation task begins immediately after takeoff. It is very important to remain oriented and maintain a high level of situational awareness. The aircraft must be flown on course and remain clear of restricted airspace.

On occasion, a pilot may be unsure of an aircraft's exact position. The first step is to make note of any discernible checkpoints on the ground. These features can be cross-referenced with those what are depicted on the map. The position of an aircraft can be determined based on heading and distance from these known points. To fly safely a pilot must be an efficient and an effective navigator.

While enroute the aircraft is flown at one of the established VFR cruising altitudes. These altitudes are designed to preclude any conflicts with IFR traffic. VFR cruising altitudes begin at three thousand five hundred feet above the ground and are measured in thousand foot increments. When flying from east to west, pilots can choose even altitudes plus five hundred feet. When flying from west to east, the pilot can choose odd altitudes plus five hundred feet.

For example, a pilot flying VFR on a westerly course from Saint Louis, Missouri to Kansas City, Missouri, can select a VFR cruise altitude of: four thousand five hundred feet MSL, six thousand five hundred feet MSL, eight thousand five hundred feet MSL, and so forth. On the return trip the appropriate choice of altitudes are: three thousand five hundred feet MSL, five thousand five hundred feet MSL, seven thousand five hundred feet MSL and above. VFR cruising rules do not apply when flying below three thousand feet AGL.

When planning for a VFR flight it is important to take into consideration, the direction and the intensity of the wind. Wind direction and intensity can vary considerably at different altitudes. A pilot can obtain wind information from the Winds Aloft Chart. Winds Aloft Charts are provided by the National Weather Service. They symbolically depict the direction and the intensity of the wind at various altitudes around the country.

Night Operations

Night operations are a unique experience. Visual acuity and depth perception are significantly reduced under nighttime conditions. The ability to distinguish form, shape, definition and detail is degraded when flying in the evening twilight or total darkness. Or eyes use different receptors to see in the dark. The rods of the eye are sensory receptors that are suited for the night. These receptors are physically located in a circular fashion around the retina. Good night vision requires an active scan. Due to the physical location of the rods in the eye a pilot must move his head and eyes continuously when flying at night.

Under low ambient conditions it is very easy to misjudge distance. One important precaution that a pilot can take before flying at night is to dark adapt. During dark adaptation, the pupils of both eyes will open wider, allowing more light to pass through the lens and into the eyes. Rods in the eyes are more sensitive and responsive to lower light thresholds.

If a pilot does not dark adapt before flying at night, both eyes will be adjusted for daytime vision. Their overall capability to see will be considerably reduced. Until their eyes dark adapt, they will not work very efficiently. An excellent example of the failure to dark adapt can be seen in a movie theater. Impatient moviegoers often enter a dark theater and set out in quick pursuit of an empty seat. The rapid transition from daylight to darkness makes it very difficult to see. The end result is a banged shin or an embarrassing fall. One easy solution is to wait a few minutes so that the eyes can adapt.

A pilot must utilize different navigation techniques at night. The ability to read a map in a dark cockpit and remain oriented requires practice. Pilots must also develop an eye for recognizing specific night navigation checkpoints. Additional preflight requirements for night flight include a properly working flashlight, a well prepared map and a close eye on the weather. The location of adverse weather and its projected course is essential information for a pilot. Fog, low level stratus clouds and reduced visibility are all contributing factors to potentially hazardous flight conditions.

A pilot flying in a remote location on a VFR flight plan should check ambient light levels to verify the amount of illumination that the moon and the stars will be providing. It is important to know what time the moon rises and sets. The moon's size and its elevation above the horizon is valuable information as well. Many times the bright light of a full moon provides illumination that rivals daytime conditions. In contrast, a night without a moon or stars may result in very dark flying conditions. It may require an instrument scan and the use of night vision devices. Cloud cover can degrade an already poor situation by blocking any ambient light from above. On the plus side, city lights do reflect brightly off the bottom of a cloud layer. These same clouds help to disburse this artificial form of light a great distance.

At night, thunderstorms are a dangerous proposition for an aviator. These large cloud formations provide a colorful display of lightning. An unwanted side effect associated with thunderstorms is the possibility of severe turbulence. A sudden jolt coupled with a rapid rate of descent is risky proposition when flying too close to a storm. Large frontal systems often contain imbedded thunderstorms. High winds associated with cold fronts move rapidly as they pass over the ground. Unrelenting rains that are released from these storms may catch an unsuspecting pilot by surprise. It is possible for aircraft damage to occur due to hail, wind shear or lightening strikes. These are some of the more serious consequences that can result if a pilot inadvertently penetrates a thunderstorm. Therefore, it is wise for a pilot to circumvent bad weather by giving it a wide berth.

Night Navigation

Night navigation requires special preflight preparation. Many terrain features and checkpoints that are utilized during daytime navigation are not visible in the dark. Therefore other techniques must be incorporated into night navigation. A pilot must also learn to recognize how the environment affects the ability to navigate at night.

For example, it is important to be sensitive to lighting and contrasts in lighting. The ability of a pilot to clearly see terrain features and navigation checkpoints is significantly influenced by the ambient light levels and the checkpoint's features. For example, when a pilot approaches an airfield located within the heart if a large city, it can be very difficult locate the runway at night. The lights of a runway are easily lost in wide expanse of bright city lights. Street lights, building lights and parking lot lights can easily outshine runway lights and make them very difficult to pick out. The pilot must continue flying toward the airfield until the outline of the runway is visible.

In a similar situation, it is equally as difficult to spot an unlit, rural airstrip at dusk. The dark black earth that surrounds the airfield closely matches the black asphalt of a single unlit runway. The pilot must use known terrain features and navigational aids in order to get the airfield in sight. The lighting system for many runways can be enabled remotely by selecting a designated frequency on the radio. To turn the lights on the pilot simply clicks the radio switch a specified number of times. The intensity of the lights can be adjusted by using clicking the microphone.

Airport Beacons

As an aid to night navigation, many airports have a rotating beacon located at the airfield. An airfield beacon is normally situated on top of a tall building or a high tower. It is comprised of two powerful lights that serve as a lone sentinel in the night. The steady flashing of an airfield beacon is an open invitation for a pilot in search of a runway. It also serves as an excellent navigation feature for pilots who are flying to a far away destination.

Civilian and military airfields are equipped with rotating beacons that operate from sunset to sunrise. The beacon is also turned on when IFR weather conditions are encountered at an airfield. Airport beacons contain a white light and a green light offset by one hundred and eighty degrees. As the beacon rotates, it emanates a flash of bright white light, followed by the flicker of a green light. Military fields utilize the same lighting system. The difference between a military airfield and a civilian airfield is the white beam. Military airfields have a split white beacon with two distinct flashes instead of one. The split white beacon helps a pilot to differentiate between civilian and military airfields.

As discussed earlier, man made features are useful checkpoints for navigating at night. The lights from the cities and nearby towns will emanate brightly into the night sky. The limits of a city are distinguished by light from the streets, moving cars and large buildings. When viewed from above, a winding road often resembles a string of lights on a Christmas tree. In contrast, a large open field reflects very little light. Dark clearings appear as a black hole surrounded by an irregular outline of lights. Successful night navigation is enhanced by the use of several techniques. For example, one way to distinguish water at night is to note how moonlight shimmers on the surface of a lake. When viewed from above, the reflected light appears to be racing across the water as though it was flying in formation with the aircraft.

Tall TV towers and high antennas are of great concern to a pilot during day and night flying periods. At night, these man made hazards are marked with bright red lights that are installed vertically on each side of these towers. Radio and TV towers higher than 1000 feet are often equipped with a large white flashing strobe light that is mounted on top of the tower.

Moonlight and More Night Flying Techniques

The moon is a important factor to consider when planning a night navigation route. The bright light emanating from a full moon can enhance the pilot's ability to navigate. On bright moon lit nights, there is sufficient light to navigate visually. Most of the objects on the ground are clearly visible.

In contrast, the brightness of a low angle setting sun has an adverse effect on a pilot's forward visibility. It can significantly hinder the ability to see clearly and to navigate. A bright sun shining in a pilot's eyes is also an annoyance. A good pair of sunglasses can be used to protect the eyes when it is necessary to navigate into the brightness of a setting sun.

Shadowing is another unique problem associated with a low sun angle. In mountainous regions, shadowing is a potentially dangerous problem. High terrain in the distance can block the low angle lighting of the sun. As a result dark shadowy regions are created, making navigation difficult in terms of obstacle avoidance.

Another dangerous scenario associated with shadowing is a case where a distant ridgeline can mask in its shadow a ridgeline that is closer and less prominent. A pilot who is unaware of this phenomenon may experience an unexpected and potentially close encounter with the ground while flying over the hidden ridgeline. Bright lights on the horizon are detrimental to the preservation of night vision. When flying at night pilots should avoid looking directly at bright lights for an extended period of time.

When flying at night it is essential for a pilot to have a flashlight in the cockpit that is easily accessible. A flashlight is essential in the event of an electrical malfunction. In the rare instances where an electrical failure occurs in an aircraft, darkness will envelop the cockpit. Many crucial instruments will be lost due to the lack of power. A flashlight is an important contingency for this unlikely occurrence.

Many daytime navigation techniques are useful at night. Prior to departure it is important to compute and plot flight information on a navigation chart for the route of flight. Data such as an estimated time enroute, the magnetic heading and distance between checkpoints is essential for accurate navigation. Night navigation routes must be planned to take advantage of "limiting features" on each leg of the flight. "Limiting features" are distinctive landmarks and recognizable terrain features that are clearly visible from the air. They are selected based on ease of use. A limiting feature is ideally linear in nature. Two lane highways and irrigation canals make excellent limiting features.

A limiting feature is a distinctive landmark that is located just beyond a designated checkpoint on the route of flight. In the event that the checkpoint is inadvertently overflown, the "limiting feature" serves as a valuable warning to the pilot. Limiting features alert a pilot when a course reversal should be initiated or if a course correction must be made, in the event that the pilot opts to continue on to the next checkpoint.

Special Use Airspace

An important part of navigation is the ability to avoid areas that have restrictions to flight. Controlled airspace is depicted on both VFR and IFR charts. The various types of controlled airspace include Restricted Areas, Prohibited Areas, Warning Areas, Military Operating Areas and Wildlife Areas. Controlled airspace exists for a variety of reasons. Many of the operations that are conducted within these areas involve dangerous activities that are potentially harmful to non-participating aircraft.

Restricted Areas

A restricted area is a designated airspace where aviation weapons delivery missions, air combat engagements and missile test firings take place. Ground based weapon systems may also fire at targets in a Restricted Area. The trajectory of the munitions passing through the air creates a dangerous situation for any unsuspecting pilot. As a result the airspace is restricted from use by general aviation. Aircraft not under positive radar control in a restricted area are not authorized to fly within a restricted area. A restricted airspace protects an aircraft from physical harm. It is a pilot's responsibility to remain clear of all active restricted areas.

Prohibited Areas

A prohibited area consists of airspace where flight is strictly forbidden. A high level clearance is required to enter prohibited airspace. Prohibited areas are designed to protect installations that are essential for national security such as the Congress, the White House and select industrial production facilities.

Warning Areas

Warning areas are located offshore. A warning area like a restricted area protects pilots from potentially dangerous activities. For example, naval vessels or military aircraft may be firing weapon systems within the confines of a Warning Area. The difference between a Restricted Area and a Warning Area is that Warning Areas extend out over international waters and their use cannot be as strictly controlled.

Military Operating Areas (MOA's)

A Military Operating Areas or MOA is a designated airspace where extensive military flight activities are conducted. See and avoid rules apply to participating aircraft and they are responsible for their own separation. Non-participating aircraft are highly encouraged to remain clear of MOA's due to the high concentration of military aircraft. The fast pace of Air Combat Maneuvering is an unfriendly environment for an unsuspecting pilot who flies into the middle of a high speed, high angle of bank, engagement. Locations adjacent to sites where a large number of military aircraft train are often designated as Alert Areas. A pilot who elects to fly through an Alert Area must be vigilant and aware. A high volume of traffic transits through an Alert Area, on their way to and from an operating MOA.

Wildlife Areas

Pilots are restricted from flying at low level altitudes over designated Wildlife Areas. Wildlife Areas should be flown over with a vertical distance of two thousand feet AGL. The airspace serves as a buffer and it is designed to protect wildlife. Wildlife Areas are typically found along coastal and flyway regions where migratory birds are prevalent. The airspace protects nesting sites and locations where rare species are present.

Restricted areas, Prohibited areas, MOA's and Warning areas are all depicted on the VFR Sectional charts. A discreet radio frequency is assigned for pilots to determine the status of these areas and to obtain a clearance for flight within this airspace.

Global Positioning Systems (GPS)

Navigating with a map by referencing key terrain features on the ground is a skill that all pilots must master. It is essential for a pilot to keep up with the exact position of their aircraft as it moves over the ground. In many cases cockpit instruments are very beneficial in providing detailed navigation and present position information to the pilot. A navigational system of great value to a pilot is the Global Positioning System or GPS.

The Global Positioning System is a satellite based navigation system designed and launched by the United States military. GPS satellites are situated in outer space and they provide pilots with very accurate, continuously updated, latitude and longitude information. The GPS system was launched in the 80's and a variety of these satellites were put into space. These satellites are capable of transmitting a continuous, discreet signal that can be detected by a functional GPS receiver.

A GPS receiver receives discreet signals from every GPS satellite that is in range of the receiver. In order for a GPS receiver to function properly, it must receive a signal from a minimum of three satellites. Using this information, the GPS can determine its exact location by processing the signals and computing the direction and distance they came from. GPS receivers are used to provide a pilot with a current latitude/longitude position and to compute heading and distance to other locations.

For example, a pilot can program the coordinates of a destination airfield into the GPS receiver. While enroute, heading and distance information will be continuously updated and displayed on the GPS screen. In addition to heading and distance information, ground speed and time enroute information is also computed.

A pilot can obtain crucial navigation information from a GPS receiver by selecting the "present position" setting. In this configuration, it provides the pilot with a continuously updated listing of the aircraft's current latitude and longitude.

Certain types of aircraft have moving map display systems installed in their cockpit. A moving map display combines map symbology with an aircraft icon that is superimposed over a map. To navigate, the pilot simply notes the position of the icon in relation to a map that moves.

GPS technology reduces pilot workload and provides a variety of important benefits. The GPS can compute and display a crosswind component. The receiver provides corrected headings for a pilot to fly in order to maintain a proper track across the ground. The accuracy of GPS is invaluable for eliminating navigation errors and saving fuel. With a GPS receiver, a pilot can fly on a direct course over a very long distance and still stay on course.

A GPS in the cockpit can be programmed with the location of a variety of airfields. These pre-programmed airfields can serve as valuable diverts in the event of bad weather at a destination airfield. Precise heading and distance information to an alternate is crucial when a missed approach must be executed. The estimated time enroute and ground speed to the designated alternate airfield is automatically computed by the GPS system. Precise ground speed computations are very important when determining fuel requirements to the alternate. A GPS lets pilots quickly evaluate the feasibility of several alternates and choose the one that is best suited for their current situation.

GPS is a technology that came of age and quickly matured during the Gulf War in Kuwait. Many ground and aviation units utilized GPS as a reliable source of information to determine present position, avoid obstacles, generate targeting information and establish rendezvous points. During desert operations there are few distinct terrain features of any significance. Navigation is very difficult and GPS systems helped to fill a void. They created a reliable way of generating definitive electronic checkpoints and they provide for more reliable methods of navigation.

GPS systems are also available to civilians. Some of the more recent GPS systems for sale include moving map displays for automobiles and navigational guidance systems for ships on the open seas. Hand held GPS receivers are available for outdoorsmen who frequently go on fishing, hunting and boating excursions.

Instrument Flight Navigation

IFR flight involves the use of different systems for navigation. When flying in the clouds a pilot cannot reference the terrain for navigation purposes. Therefore navigation must be conducted by using various flight instruments in the cockpit. The Federal Airways System was designed for this purpose. An airway resembles a highway in the sky. Pilots can navigate safely along an airway under IFR flight conditions by utilizing published IFR navigation charts.

The Federal Airways System originated in the early 1920's, when a visual navigation system was designed for pilots who were required to fly over remote stretches of land at night. Large bonfires were built along the way in order to illuminate the proper route of flight. Through the darkness a bright flame was visible by the pilot. These fiery markers served as welcome reference points that lead the pilots to their destination. Extended flights at night became a safer proposition once this system was put into place.

Over a period of time fires were replaced by light beacons, and the beacons were eventually replaced by an electronic navigation system. The advantage that an electronic system has over a visual one is the fact that the pilot can fly and navigate without any ground reference. The difference is that a radio beacon emits an electronic signal instead of visible light.

Instrument equipped aircraft flying at altitude use these navigation signals to navigate accurately. Modern day electronic stations are called navigational aids or NAVAIDs. The function of a NAVAID is to transmit three hundred and sixty discreet signals. Each signal is called a "radial". Radials are equivalent to the headings on a compass and the signal pattern created by a NAVAID station resembles the spokes on a wheel. The 360 radials that scribe a full circle around the station can serve as a potential highway on the modern day airways system. IFR aircraft navigate on radials by proceeding from one NAVAID station to the next. The ability of an aircraft to receive a specific navigation signal is based on several factors that include, the height of the terrain surrounding the NAVAID and the height of an aircraft above the ground, the type of electronic equipment installed in the aircraft and the signal strength.

Various instruments are used in the cockpit when navigating on an IFR flight. These instruments provide important information about the relative position of the aircraft from a NAVAID. An aircraft's position is determined in the cockpit with a gage that depicts what radial the aircraft is on. In some cases, the same instrument reveals how far the airplane is from the NAVAID station.

One type of instrument that is used to express this information is called an RMI or Radio Magnetic Indicator. The RMI is designed with a rotating compass disc mounted on the face of the gage. The disc is marked on its outer edge with 360 degrees of compass headings. The RMI card has a rotating compass indicating system that continuously displays the aircraft's magnetic heading.

The heading of the aircraft is indicated by a fixed indexer that is located at the top of the RMI gage. The fixed indexer indicates present heading when the aircraft is straight and level. When the aircraft is in a turn the RMI card turns spins beneath the fixed indexer. The rate that the compass card spins is based on the aircraft's angle of bank. At a greater angle of bank the compass card will turn faster. Refer to Figure (8) for an illustration of an RMI gage.

The navigation needle is another important component of the RMI gage. The navigation needle is mounted directly above the RMI compass card. The navigation needle is designed to continuously points toward any NAVAID that is tuned into the receiver. In order for a pilot to fly directly to a NAVAID, the pilot turns the aircraft so that the head of the needle is aligned with the fixed indexer on the top of the gage.

The basis for IFR navigation is built on this concept. In terms of a real world example, a pilot may be instructed by approach control to proceed directly to an assigned NAVAID. The aircraft is turned in the shortest direction so that the head of the needle is positioned underneath the fixed indexer. When the two are aligned the aircraft will be proceeding toward the selected NAVAID station. Keep in mind that this heading is a "no wind" heading and there are no corrections for wind. A crosswind component will affect the course of the aircraft as it flies toward the NAVAID. The movement is detected when the navigation needle drifts out and moves away from the fixed indexer.

Wind affects the track of an aircraft over the ground. In the case of a crosswind the pilot must compensate by flying the aircraft into the wind. This correction is known as a "crab". A crab is designed to keep the aircraft on course. To initiate a crab the aircraft is turned into the wind so that an offset heading can be flown. The proper ground track is maintained by pointing the nose of the aircraft into the force of the crosswind.

To determine what radial the aircraft is on, simply references the tail of the navigation needle. The tail of the needle represents the actual position of the aircraft in relation to the station. The following is an example of how a pilot will use the tail of the needle to accurately navigate. Let's assume that an aircraft is located southeast of a NAVAID on the one five zero degree (150) radial. In this example, we will say that the pilot is flying from south to north and will pass the NAVAID to the east. As you can see, the aircraft is not heading directly toward the NAVAID. The RMI gage will indicate a northerly heading of three six zero degrees (360). As the aircraft flies north, the tail of the needle will rise and move through the one five zero degree (150) radial, past the zero nine zero (090)degree radial and up through the zero three zero (030) degree radial and so forth.

Refer to Figure (9) to help alleviate any confusion that may arise from these examples. The tail of the needle indicates an aircraft's present position. The head of the needle indicates where the NAVAID station is located in relation to the aircraft. There are many moving parts to an RMI gage. All of the moving parts in an RMI gage provides a pilot with essential information that helps to make navigation easier.

A Crosswinds Effect on Navigation

A crosswind is a lateral force that influences the heading of an aircraft. To determine if a crosswind component exists, a pilot maintains a no wind heading and notes any drift on the navigation needle. Drift occurs when the tail of the needle moves away from a designated radial. Wind may exist but it may not affect the aircraft laterally. A direct headwind or tailwind will increase or decrease an aircraft's rate of travel over the ground but it will not cause any lateral drift.

A crosswind component is displayed when the navigation needle drifts away from the desired radial. The rate of displacement is used to determine the strength of the crosswind component. Corrections for drift are intended to place the aircraft back on the designated radial. Once the aircraft is back on track some of the initial crab must be taken out. If it is not reduced, the airplane will fly through the radial and overshoot to the other side of the course line.

For example, if the pilot is instructed to fly inbound to the NAVAID, on the zero nine zero (090) degree radial and the tail of the needle begins drifting upward toward the zero eight five (085) degree radial, a crosswind is blowing from the south. The wind is pushing the aircraft sideways, from south to north.

In another example, the pilot notes that the tail of the needle is moving from the zero nine zero (090) degree radial toward the zero nine five (095) degree radial. In this case the crosswind is blowing from north to south.

Refer to Figure (10) to review how a crosswind effects the ground track of the aircraft and how a crab is used to overcome unwanted drift.

IFR navigation is conducted by employing instrument flight techniques. Navigation stations located around the world serve as the foundation for this method of travel. After takeoff, a pilot intercepts an assigned radial and flies outbound to a specific point along the route. At that point, the next NAVAID station is tuned in. The needle on the RMI swings around and begins pointing to the new NAVAID station that is located in front of the aircraft. The head of the needle is used to navigate along that radial and to maintain a proper ground track. When the aircraft passes over the next NAVAID station, the navigation needle spins around for 180 degrees and the pilot navigates outbound, using the tail of the needle.

In addition to heading (azimuth) information, several navigation receivers are capable of providing distance information. Distance is displayed on the RMI gage as well. Distance Measuring Equipment, known as DME works by transmitting a signal from the aircraft to a NAVAID station. The station immediately responds to the query by sending a return signal back to the aircraft. Distance from the station is determined by measuring the time that it takes for the signal to travel from the aircraft to the NAVAID and back to the aircraft. DME is expressed in nautical miles. A nautical miles is eight hundred feet longer than a statute mile (6080 feet vice 5,280 feet). DME is a very useful way to determine the exact position of an aircraft in relation to a NAVAID station.

IFR Charts

The Federal Airways System uses radials to connect one NAVAID station with another. IFR enroute charts and pilot Jepson Manuals depict published airways segments along with pertinent information such as NAVAID frequencies, minimum enroute altitudes, intersections and divert airfields. Refer to Figure (11) for a sample IFR chart.

Information provided on IFR charts is useful during preflight planning and while airborne. An IFR chart displays mileage for each flight segment. Total mileage between NAVAIDs is depicted in a box that is located next to the radial that defines the airway. An airway is the segment between two NAVAID stations. Intersections are also depicted on IFR charts. An intersection is a point in space where two or more airways cross. Intersections are labeled with five letter names. An example of the name of an intersection is "RAVEN" intersection.

Civilian and military IFR Charts depict separate high and a low altitude route structures. The low altitude IFR enroute charts are more detailed and depict a much smaller area over the ground. More airfields and NAVAIDS are also displayed on a low altitude chart. The Federal Airways System is divided into two parts. The first part is the Low Altitude Airways System. Altitudes in the Low Altitude Airways System are separated in increments of one thousand feet. For example, aircraft flying west to east are expected to file at odd altitudes, such as five thousand feet MSL, seven thousand feet MSL and so forth. Aircraft flying east to west are expected to file for even altitudes such as six thousand feet MSL or eight thousand feet MSL.

The low altitude Federal Airway System is contained within the airspace that extends from twelve hundred feet above the ground to eighteen thousand feet above sea level. Each route is labeled by with single letter followed by a one to three digit number. Low Altitude routes begin with the letter "V," followed by the route number, such as V123. The low altitude route structure is also referred to as the "Victor" airways.

Jet routes on the other hand are designed for high altitude operations. A typical route segment is longer and more direct. Jet routes are depicted on IFR High Altitude Charts. The high altitude route structure begins at eighteen thousand feet MSL and extends up to forty-five thousand feet MSL. Jet routes are labeled just like the low altitude system only the letter "J" replaces the letter "V". As an example, "J32" represents jet route 32. Assigned altitudes are called "Flight Levels".

IFR Clearance

Prior to taxiing, a pilot must request an enroute clearance. The clearance defines the expected route of flight based on information provided in the filed flight plan. A pilot is instructed by Air Traffic Control to fly a route specified in the enroute clearance. Clearances are built based on a computer analysis of the projected traffic along a route of flight. When Clearance Delivery reads the clearance information to the pilot, the pilot writes the information down and compares it with the filed flight plan. If the routing has changed, the pilot must reevaluate the effect of these changes and determine how they will impact fuel consumption and total time enroute. If there is a problem or there is insufficient fuel onboard the aircraft, the pilot must request an amended route of flight or the aircraft must be shut down in order to take on additional fuel. When a pilot is unsure of any portion of the clearance, the clearance must be read back so that any misunderstandings can be clarified.

Instrument Approaches

IFR instrument charts, instrument approach plates and navigation publications are carried by pilots during each flight. These navigation publications are updated regularly and provide detailed information on the procedures required to fly safely in IFR flight conditions. An instrument approach plate is like a road map in the sky. It depicts the altitudes that the pilot must fly and the courses that must be flown to get down to the runway.

Approaches are named after the navigational aid that is used during the approach. The magnetic heading of the runway is also included. For example, the VOR approach to runway 12 Right at Steamy Acres airfield utilizes a VOR as the navigational aid and terminates with a landing on runway 12 Right. The name of the approach is the "VOR12R" approach. The number 12 represents a magnetic heading of one hundred and twenty (120) degrees. The R represents the right runway at a 2 parallel runway airfield.

To minimize confusion, there are large white numbers painted on the approach end of each operational runway. These numbers indicate the magnetic heading of the runway and help a pilot verify from the air which one is the correct runway for landing. Closed runways have a series of large yellow X's painted down the center of the runway. These X's are painted along the entire length of the runway so that there can be no doubt that a landing should not be attempted unless the pilot is experiencing an emergency.

Approach plates depict important information in order for a pilot to make a safe letdown to a landing. The information is presented in a variety of ways. A birds eye view and a cross sectional view of the approach are both on the approach plate. The pilot uses these two profiles to navigate the aircraft along a winding, descending, invisible path to a safe landing. Occasionally an instrument approach must be flown in the clouds, down to approach minimums for the runway in use. Information such as segment altitudes, authorized descent points, the final approach course and the missed approach point are all included on the approach plate. Refer to Figure (12) for an example of an actual approach plate.

Additional information normally displayed on an approach plate includes the airport elevation, runway length, weather minimums and the runway layout. Before commencing an approach, a pilot must be very familiar with the entire procedure. Deviation from any published altitudes or headings must be carefully avoided unless these variances are approved by approach control.

During periods of inclement weather it is even more essential for a pilot to comply with the published approach instructions. When aircraft are flying in clouds the pilots are unable to see and avoid other aircraft. Therefore air traffic controllers must provide sequencing and separation in a high density traffic area. The air traffic controller must constantly monitor all activity within their assigned sector and manage the flow of aircraft through their designated airspace. Controllers assist pilots by providing crucial navigational information and recommendations for severe weather avoidance.

Many large commercial aircraft have sophisticated navigation and instrument landing systems that provide for the capability to land in thick fog. Vertical and horizontal visibility is a critical consideration during the landing phase of a flight. On the final portion of an instrument approach, the pilot must be able to break out of the clouds and visually acquire the runway. Sometimes, this has to be accomplished in a relatively short period of time. Runway centerline lights are helpful for a pilot. They serve as a reference in order to help keep the aircraft properly aligned with the middle of the runway. Large white center line stripes are also painted down the runway. During periods of low visibility and at night, the white centerline lights are lit. They also help a pilot properly distinguish a runway from other visual illusions such as a brightly lit highway.

Sophisticated onboard computers and navigation equipment provide a pilot with the capability to land a large commercial aircraft without touching the flight controls. During a coupled approach, the flight control